The invention relates to tire building apparatus and particularly to such apparatus which includes an expandable and retractable tire building drum with axially movable bead carrier assemblies positioned at the ends of the drum.
A tire building apparatus as described, for example, in U.S. Pat. No. 4,007,081 comprises a radially expandable cylindrical drum, a pair of axially movable bead carrier assemblies, one at each end of the drum, and fluid actuated means which positively drives or move the carrier assemblies axially toward and away from the ends of the drum. Each of the carriers includes radially outwardly movable bead lock clamps which are also positively driven or moved.
When building a tire on such a tire building apparatus the components of a tire carcass are arranged around the exterior of the drum and carrier assemblies and tire beads are placed over the carcass on each carrier assembly. The bead lock clamps are actuated to move radially outwardly to lock and support the beads in position on the tire carcass. The drum is then expanded radially outwardly while a shaft is rotated by an air actuated clutch to positively move each carrier assembly axially inwardly towards the ends of the drum to allow expansion of the drum. After completion of building the tire (e.g. by placing the belt assembly and tread around the expanded drum), the drum is retracted and the carriers are returned to their original locations when the air actuated clutch rotates the shaft in the opposite direction.
To positively move each carrier assembly axially inwardly toward the ends of the drum or axially outwardly away from the ends of the drum requires separate actuation devices to move each carrier assembly and energy in the form of air pressure to operate such devices.